1. Field of the Invention
The present invention relates to an image forming apparatus, and more particularly, to a paper-feeding device capable of moving a pick-up device up and down in cooperation with a mounting/removing operation of a paper-feeding cassette of a dam division type in an image forming apparatus.
2. Description of the Related Art
Generally, image forming apparatuses, such as a printer, a copying machine, or a facsimile machine, sequentially pick-up and convey an uppermost paper sheet of a paper pile loaded in a paper-feeding cassette detachably mounted at a body of the image forming apparatus to an image forming section, thus forming an image.
FIG. 1 is a perspective view schematically showing a conventional image forming apparatus and a paper-feeding device thereof. FIG. 2 is a perspective view showing the conventional paper-feeding device in FIG. 1. FIG. 3 is a detailed plan view showing the pick-up device in FIG. 2.
With reference to FIG. 1, the conventional paper-feeding device includes a paper-feeding cassette 20 and a pick-up device 30. The paper-feeding cassette 20 loads plural sheets of paper. The pick-up device 30 is installed at an upper side of a paper-feeding cassette mounting section 10, and conveys the sheets of paper loaded in the paper-feeding cassette 20 to an image forming apparatus (not shown). The paper-feeding cassette mounting section 10 is provided at a body 1 of the image forming apparatus.
The pick-up device 30 includes a pick-up roller 31, an up-down section 32, and a driver 33. The pick-up roller 31 conveys the paper in a direction perpendicular to a removing direction of the paper-feeding cassette 20. The up-down section 32 drives in cooperation with a mounting and removing operation of the paper-feeding cassette 20, and moves the pick-up roller 31 up and down to the paper-feeding cassette 20. The driver 33 provides the rotational driving force to the pick-up roller 31 to sequentially convey the paper loaded in the paper-feeding cassette 20 in the base 5 of the body 1.
The pick-up roller 31 is installed to pick up the paper in a direction perpendicular to the removing direction of the paper-feeding cassette 20. As shown in FIG. 1, the paper-feeding cassette 20 is mounted and removed to and from a direction perpendicular to a pick-up and transferring direction of the paper for the body 1 of the image forming apparatus.
Referring to FIGS. 2 and 3, the up-down section 32 includes a cam projection 21, a support frame 35, a cam lever 40, a first rotating shaft 42, a locking arm 50, and a pick-up bracket 60. A curved cam portion of the cam projection 21 protrudes to one front end of the paper-feeding cassette 20. The support frame 35 is installed at the paper-feeding cassette mounting section 10 of the body 1. The cam lever 40 is installed at the support frame 35. Upon removing the paper-feeding cassette 20 from the paper-feeding cassette mounting section 10, the cam lever 40 rests on the cam projection 21 and is rotated by the cam projection 21. The first rotating shaft 42 is rotated in cooperation with the cam lever 40. The locking arm 50 is rotated in cooperation with, and in a direction opposite to a rotating direction of, the cam lever 40. The pick-up bracket 60 is rotatably connected to a third rotating shaft 61 installed at the support frame 35, and up and down movement of the pick-up bracket 60 is restricted by the locking arm 50.
As shown in FIGS. 2 and 3, the cam lever 40 is installed to be resiliently biased to the paper-feeding cassette 20 by the first coil spring 41, and is connected to the locking arm 50 through the first rotating shaft 42. The first coil spring 41 is installed at the body 1.
When the locking arm 50 rotates, a hook pin 51 provided to a free end of the locking arm 50 connects with the paper-feeding cassette 20 of the pick-up bracket 60 to restrict up and down movement of the paper-feeding cassette. Accordingly, the pick-up bracket 60 cooperates with the hook pin 51, and is moved up and down.
A free end portion of the pick-up bracket 60 rotatably supports the pick-up roller 31, and is installed to be resiliently biased to the paper-feeding cassette 20 by a second coil spring 62. The second coil spring 62 is installed at a support member 62a of the support frame 35. When the paper is conveyed, the pick-up roller 31 conveys the paper while pressing the uppermost sheet of paper loaded in the paper-feeding cassette 20 at a suitable pressure.
Furthermore, the pick-up bracket 60 includes a protrusion member 38 which protrudes downward from the pick-up bracket 60. The protrusion member 38 contacts a hook member 72 to be described below, thus restricting an operation of the pick-up bracket 60.
The driver 33 of the pick-up device 30 includes a driving motor 34 and a power transmission section (not shown). The driving motor 34 is installed at the support frame 35, and produces a rotational driving force. The power transmission section is installed inside the pick-up bracket 60, and provides the rotation rotating force of the driving motor 34 to the pick-up roller 31.
A locking/unlocking section 36 includes a solenoid driver 70, a third rotating shaft 71, and the hook member 72. The solenoid driver 70 is installed at the support frame 35. An operation of the solenoid driver 70 controls whether the solenoid driver 70 contacts with a connecting member 70a that is provided at one side of the paper-feeding cassette 20. The second rotating shaft 71 is installed at the support frame 35, and rotates by the operation of the solenoid driver 70. The hook member 72 is provided at one end of the second rotating shaft 71. As the second rotating shaft 71 rotates, the hook member 72 contacts and locks/unlocks the pick-up bracket 60.
That is, upon mounting the paper-feeding cassette 20 into the paper-feeding cassette mounting section 10, the cam projection 21 and the cam lever 40 contact each other. Further, the connecting member 70a provided at the one side of the paper-feeding cassette 20 comes in contact with the solenoid driver 70. At this time, the hook pin 51 is released due to the contact between the cam projection 21 and the cam lever 40, and the operation of the solenoid driver 70 rotates the second rotating shaft 71, and the pick-up bracket 60 is released, thus permitting the pick-up bracket 60 to be lowered.
When the paper-feeding cassette 20 is removed from the paper-feeding cassette mounting section 10, the cam projection 21 no longer is in contact with the cam lever 40, and the solenoid driver 70 no longer contacts the connecting member 70a provided at the one side of the paper-feeding cassette 20. Consequently, the pick-up bracket 60 is raised according to a rotation of the hook pin 51 that is engaged with the cam lever 40. Furthermore, the hook member 72 constrains the protrusion member 38, immobilizing the pick-up bracket 60.
Hereinafter, an operation of the conventional paper-feeding device will be described.
As the paper-feeding cassette 20 in which paper is loaded is inserted into the paper-feeding cassette mounting section 10 of the body 1, the cam lever 40 contacts the cam projection 21 provided at the front end of the paper-feeding cassette 20, and is thus rotated upward. At the same time, the locking arm 50 is rotated downward.
Accordingly, the immobilized state of the pick-up bracket 60 due to the hook pin 51 provided at the free end of the locking arm 50 is released, whereas the immobilized state of the pick-up bracket 60 due to the hook member 72 is maintained. As a result, the pick-up bracket 60 is maintained in an initial state.
When the paper-feeding cassette 20 is further inserted into the paper-feeding cassette mounting section 10, the connecting member 70a provided at one side of the paper-feeding cassette 20, and the solenoid driver 70 contact each other. At this time, the solenoid driver 70 operates to rotate the rotating shaft 71, and the state of the pick-up bracket 60 immobilizing the protrusion member 38 is released. Accordingly, the pick-up bracket 60 descends by a self-weight, and contacts the uppermost sheet of paper loaded in the paper-feeding cassette 20.
At this time, as the pick-up bracket 60 is resiliently biased downward by a tensile force of the second coil spring 62 installed at a front end of the pick-up bracket 60, the pick-up roller 31 comes in contact with the uppermost sheet of paper loaded in the paper-feeding cassette 20, while pressing it at a suitable pressure.
In such a state, when a printing command is inputted to an image forming apparatus, a rotational driving force of the driving motor 34 is transferred to the pick-up roller 31. The pick-up roller 31 sequentially conveys the paper loaded in the paper-feeding cassette 20 by using the rotation driving force of the driving motor 34, so that a printing operation begins.
Through the above-mentioned operations, after the paper loaded in the paper-feeding cassette 20 has been used, to load a new paper pile therein, the paper-feeding cassette 20 is removed from the paper-feeding cassette mounting section 10. Upon removing the paper-feeding cassette 20 from the paper-feeding cassette mounting section 10, the interference between the cam projection 21 and the cam lever 40 is released, so that the cam lever 40 rotates downward by a restoring force of the first coil spring 41, and simultaneously the locking arm 50 rotates upward. Accordingly, the pick-up bracket 60 also ascends via the hook pin 51 that is provided at the free end of the locking arm 50. As the paper-feeding cassette 20 is removed from the paper-feeding cassette mounting section 10, the contact between the connecting member 70a provided at one side of the paper-feeding cassette 20 and the solenoid driver 70 is released. At that time, the solenoid driver 70 operates to rotate the second rotating shaft 71. The hook member 72 becomes engaged with the rotation of the second rotating shaft 71 and restricts a protrusion member 38 that is provided at the pick-up bracket 60.
According to the conventional image forming apparatus and the paper-feeding device as described above, in the case wherein upward and downward operation of the pick-up bracket 60 is restricted due to the hook member 72, in cooperation with the solenoid driver 70, upon mounting the paper-feeding cassette 20 in the paper-feeding cassette mounting section 10, the pick-up bracket 60 descends in a state in which the paper-feeding cassette 20 is not completely inserted into the paper-feeding cassette mounting section 10. Then, the pick-up roller 31 descends to pull and twist the uppermost sheet from the paper loaded in the paper-feeding cassette 20. When a printing process starts and the paper is picked-up, a paper skew or jam occurs. Furthermore, upon removing the paper-feeding cassette 20 from the paper-feeding cassette mounting section 10, the pick-up roller 31 ascends and may be caught on the paper-feeding cassette 20, resulting in a breakdown of a part of the pick-up roller 31.